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Akrapovic carbon technical question


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FrostHazer

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Sep 21, 2014
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hello, I was wondering why the akrapovic carbon is the only exhaust that it's pipe is curved and twisted that way and why other exhausts, even akra titanium, dont do that.
gasses are more difficult to go out that way, it creates more backpressure and that has a negative effect...Im I wrong?
 
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If you mean the pipes from the engine to silencer "loose description" then they are done that way to equalise
the lengths of the pipes so both cylinders see the same length of exhaust and or so that one exhaust pulse
helps extract the next.
 
Ralph said:
If you mean the pipes from the engine to silencer "loose description" then they are done that way to equalise
the lengths of the pipes so both cylinders see the same length of exhaust and or so that one exhaust pulse
helps extract the next.
Click to expand...

I mean the loop it makes,like a circle, right before the silencer.
View attachment 1385
 

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  • Akrapovic_S-Y7R2-AFC_MT-07_Exhaust_Scarico_Pot_Auspuff.webp
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My thoughts are, it could be the loop has been added to tune the exhaust for back pressure (more accurately tune the exhaust for gas scavenging). There are, plenty of articles on the subject just google exhaust scavenging (high velocity & low restriction of exhaust gases "pulls" them out the cylinder during the exhaust phase which is a good thing but too many restrictions or too big a diameter or long an exhaust pipe slows down the exhaust gases which is a bad thing)

But then sometimes the exhaust is lengthened / shortened to change the noise output (think Harley davidsons and straight through pipes), i guess adding a loop is one way of doing this with out adversely affecting exhaust gas flow (which you would with more baffles / baffle material) or the overall size of the exhaust yet the pipe still gets longer.

........ Or maybe it was just a neat solution to exhaust mounting without a hangar bracket being used on what is a relatively expensive upgrade?

Anyone got any other theories, I'm curious to know why the carbon version has been looped.
 
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Yes, Nuggets is definitely right, they did this to get the required header length for maximum performance.

The carbon version is not 'street legal' like the titanium (like anyone cares lol), so they did everything on this version to get max torque and horsepower.
However i think you wouldn't notice a difference on a street bike. but you probably would on a bike with a good intake setup (free flowing filter and fuel commander).

Regards,
Dutchman
 
The Dutchman said:
Yes, Nuggets is definitely right, they did this to get the required header length for maximum performance.

The carbon version is not 'street legal' like the titanium (like anyone cares lol), so they did everything on this version to get max torque and horsepower.
However i think you wouldn't notice a difference on a street bike. but you probably would on a bike with a good intake setup (free flowing filter and fuel commander).

Regards,
Dutchman
Click to expand...

ok, but its the only exhaust that have that loop. even exhausts that claim more hp gain like two brothers dont have that. all other racing exhausts have much shorter pipe...that's what i dont get.
 
eventually the best thing to do after mouting a new exhaust that changes the flow and pressure - will profit very much on the positive side if you have the ECU remapped and run in at a DynoJet. Im paying 600£ for this job, which includes the upgrade of a Powercommander V.

I had my IXIL Hyperlow on for 4 days before storring it for the winter. It "farted" when i released the throttle - some people like the small explosions in the exhaust cause it sounds cool, but its not the most optimale setting for the engine. So thats why i decided to have this treatment done :)
 
Ok
All exhaust manufacturers claim they make more HP.
Some points: The loop ( snail pipe) is done to put pipe length in where their is little room usually, but in this case it is a styling exercise so people don't make comments like " I don't like the long pipe". See later. It also helps centralize weight , although as both the can and the pipe weigh stuff all, it would be a marginal improvement.
Power robbing: Have a look ate the MotoGp Honda V4's. The pipes from the rear cyls are a very similiar snail shape under the back seat. If it was power robbing they would not be doing it. The gas slug pretty much doesn't notice the bend unless it is too tight a radius.
Length: The MT07 is a ( relatively) low reving motor. The motor is designed for torque, not high end HP, so the cam timing will be somewhat shallow i am guessing. I don't know the last bit as fact, as I am still trying to find out exactly what the cam angles are. Haven't had the bike long enough to degree it. The lower the revs AND the shallower the cam timing for the exhaust, the longer the pipe has to be for tuned length. My completely off the top of the head guess for this bike is longer than 45inches ( about 114cm) valve to pipe end total length. That is way longer than the stock pipe or the pseudo OEM Akra. The Snail pipe carbon is probably a closer length to ideal. As usual it is a Yamaha style bit to make the bike look like a race bike ( which it isn't). MotoGp bike rev to a current limit is 17500 ( I think, blame wiki if it isn't) and deep valve timing, which make the tuned lengths VERY short so the "mufflers" end up more under the engine from the front cyl.
IMPORTANT NOTE: No two into one exhaust system will work for maximium obtainable power on this bike ( actually there is a way but you end up with a huge expansion box at the end of the pipes) . The cranks are at 90 (270)deg so the exhaust pulse will be exactly badly out of phase. Vtwins and offset cranks like the MT07 need 2 into 2 systems for optimium performance. And that just doesn't look cool nowdays..
On the road it won't matter much, but if I was racing one it would have a 2-2 if the rules allowed. If they didn't allow i, I would race one.
 
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gregjet said:
Ok
All exhaust manufacturers claim they make more HP.
Some points: The loop ( snail pipe) is done to put pipe length in where their is little room usually, but in this case it is a styling exercise so people don't make comments like " I don't like the long pipe". See later. It also helps centralize weight , although as both the can and the pipe weigh stuff all, it would be a marginal improvement.
Power robbing: Have a look ate the MotoGp Honda V4's. The pipes from the rear cyls are a very similiar snail shape under the back seat. If it was power robbing they would not be doing it. The gas slug pretty much doesn't notice the bend unless it is too tight a radius.
Length: The MT07 is a ( relatively) low reving motor. The motor is designed for torque, not high end HP, so the cam timing will be somewhat shallow i am guessing. I don't know the last bit as fact, as I am still trying to find out exactly what the cam angles are. Haven't had the bike long enough to degree it. The lower the revs AND the shallower the cam timing for the exhaust, the longer the pipe has to be for tuned length. My completely off the top of the head guess for this bike is longer than 45inches ( about 114cm) valve to pipe end total length. That is way longer than the stock pipe or the pseudo OEM Akra. The Snail pipe carbon is probably a closer length to ideal. As usual it is a Yamaha style bit to make the bike look like a race bike ( which it isn't). MotoGp bike rev to a current limit is 17500 ( I think, blame wiki if it isn't) and deep valve timing, which make the tuned lengths VERY short so the "mufflers" end up more under the engine from the front cyl.
IMPORTANT NOTE: No two into one exhaust system will work for maximium obtainable power on this bike ( actually there is a way but you end up with a huge expansion box at the end of the pipes) . The cranks are at 90 (270)deg so the exhaust pulse will be exactly badly out of phase. Vtwins and offset cranks like the MT07 need 2 into 2 systems for optimium performance. And that just doesn't look cool nowdays..
On the road it won't matter much, but if I was racing one it would have a 2-2 if the rules allowed. If they didn't allow i, I would race one.
Click to expand...

thanks for your answer!
 
An interesting side note.: I saw in the magazine today a picture of the new Yamaha YZFR1 . They also have a crossplane ( 90/270 deg) crank but on a 4. They appear to have used a setup I figured out a while ago when I was designing a system that would work on a CBR250RR I used to race. Because the pipes to first join on a 4-2-1 header are so short you simple cannot physically join them there ( 16500rpm max HP point) as the outer 2 pipe have to join together, and you have to go around the inner pipes. So I treated it as a full length set of 4 singles and designed a dump box big enough for the cycls. to think they were opening into a open atmosphere and took the tail pipe as a bleed down only. Not too hard to do because each cyl is only 62cc and the box didn't have to be very big. The new yammy has the same problem as the MT07 with the out of phase pulses so they have joined each of the two 180deg cycls pipes together, then put them into a split box before joining into a single outlet. Hopefully one day some pipe maker will do similar for the MT. 2 into 2 OR 2 into a dump box then out. It WILL make better power.
 
Hello,

I want to ask 2 question about Akra Carbon.
Ive just instaled yesterday that exhaust. (geeeezzz so perfect sound)
BUT!
1. When i was taking down old exhaust betwen engine and exhaust was 2 o-rings, but akra in box dont have it, even in installation guide its nothing about that. Did you install that 2 old o-rings??
2. After fittin new exhaust and done 10 km, i was standing on red light - and touch a little throttle and engine just get OFF ; oooo ??? Never done before on old exhaust got any idea what the problem?


Thanks,
Dev.
 
When I installed the carbon exhaust, I used the two o-ring with the install of the exhaust. As for the cutting out it could be just down to the problems most people are having anyway. However saying that I never really had a problem with cutting out. After I installed the exhaust I had it on tick over up until the point the fan came on just so that in my head the air/fuel would adjust itself to the exhaust (wether that worked or not who knows) and I will do the same when I fit the dna air filter just so the ecu knows about the changes. [emoji79]
 
dev said:
1. When i was taking down old exhaust betwen engine and exhaust was 2 o-rings, but akra in box dont have it, even in installation guide its nothing about that. Did you install that 2 old o-rings??
Click to expand...

Yes and yes again!! The O-rings are the exhaust gaskets and you definitely need these to provide a seal between the engine and exhaust. TBH if you haven't installed them I'd be surprised if you didn't hear it blowing quite badly around the exhaust manifold area.
 
I'm with torque on that one. I fitted new gaskets, they are very soft and compress very easily. I have the long arrow system, its stalled on me in exactly the way you describe. Then left fumbling for the non-intuitive starter at the lights:D
 
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